17、mint UI Tabbar选中后怎么改变icon图标

<mt-tabbar v-model="selected">
            <mt-tab-item id="首页">
                <img slot="icon" v-show="!(selected==='首页')" src="../assets/home_icon.png">
                <img slot="icon" v-show="selected==='首页'" src="../assets/home_icon_selected.png">
                首页
            </mt-tab-item>
            <mt-tab-item id="订单">
                <img slot="icon"  v-show="!(selected==='订单')" src="../assets/order_icon.png">
                <img slot="icon" v-show="selected==='订单'" src="../assets/order_icon_selected.png">
                订单
            </mt-tab-item>
            <mt-tab-item id="发现">
                <img slot="icon" v-show="!(selected==='发现')" src="../assets/find_icon.png">
                <img slot="icon" v-show="selected==='发现'" src="../assets/find_icon_selected.png">
                发现
            </mt-tab-item>
            <mt-tab-item id="我的">
                <img slot="icon"  v-show="!(selected==='我的')" src="../assets/person_icon.png">
                <img slot="icon" v-show="selected==='我的'" src="../assets/person_icon_selected.png">
                我的
            </mt-tab-item>
        </mt-tabbar>